1. Field of the Invention
The present invention relates to a wire bonding machine and, more specifically, to a wire bonding machine capable of removing particles from a capillary and a method for cleaning the bottom tip of the capillary.
2. Description of the Related Art
Generally, a wire bonding machine serves to electrically couple a semiconductor die to a circuit board (or a lead frame) by using wires. A capillary, having a pipe shape, is mounted to the wire bonding machine to handle fine wires. By using the capillary, one end of the wire is ball-bonded to the semiconductor die and the other end of the wire is stitch-bonded to the circuit board. That is, the wire bonding machine furnishes a discharge flame with the wire. The discharge flame extends to the bottom end of the capillary at a predetermined distance. Thereafter, the wire bonding machine allows the capillary to move toward the semiconductor die and then, furnishes ultrasonic waves with the capillary, so that the ball is bonded to the semiconductor die. Next, the wire bonding machine allows the capillary to move toward the circuit board and furnishes ultrasonic waves with the capillary again, so that the other end of the wire is bonded to the circuit board. After the stitch bonding of the wire, the wire is cut from the circuit board and the above process is repeated again.
In the meantime, the capillary, especially the capillary tip is under various severe circumstances. That is, the capillary tip is applied to the discharge flame and is contacted with the fused portion (ball) of the wire. Further, the capillary tip is directly and physically contacted with the semiconductor die and circuit board. Moreover, where the capillary is contacted with the semiconductor die and circuit board, since the ultrasonic wave energy is concentrated on the capillary tip, the circumstances becomes more critical.
As such, the more wire bonding that is performed, the more various foreign matters are accumulated on the capillary tip. The capillary particles itself based on the discharge flame and various metal particles based on the semiconductor die and the circuit board are irregularly accumulated on the capillary tip.
Since various particles may accumulate on the capillary tip, and since the tip shape of the capillary is not regular, various irregularities in the wire bonding process may be generated. This is especially true at the stitch bonding area of the wire. That is, since the size of the ball bonding area is much larger than the diameter of the wire, because the size of the stitch bonding area is similar to the diameter of the wire, the irregularities are mainly generated at the stitch bonding area. The dimension of the stitch area is only approximately 1-20% of that of the ball bonding area. Accordingly, if various particles are accumulated on the capillary tip as described above, since the size of the stitch bond area becomes smaller, the irregularities of the wire bonding process can often be generated.
In order to solve the irregularities of the wire bonding process owing to the capillary, the capillary is periodically separated from the wire bonding machine and cleaned. For example, the capillary is treated with chemicals, so that the various particles are removed from the capillary. Here, since the chemicals can damage the capillary, the capillary should necessarily be examined with the naked eye, after the chemical treatment. However, the chemical treatment of the capillary takes a long time and the capillary itself can be damaged according to circumstances. Moreover, because the chemicals usually have a strong acidity, it can bring about an environment pollution problem.
Instead of using the chemicals as above, there is a method where an operator physically cleans up the capillary tip by using a soft brush. However, in actuality, it is very difficult to clean up the very small capillary by the brush and the like. Furthermore, since the operation is manually performed, the removing measure of the particle varies per the capillary, so there is difficulty in reusing the capillary.